I would add a Buck Boost Converter to expand battery range. otherwise, looks good

I would add a buck boost converter to drop the voltage when to high, and boost it when to low. it extends battery lifehttps://www.banggood.com/5pcs-DC-DC-Boost-Buck-Adjustable-Step-Up-Step-Down-Automatic-Converter-XL6009-Module-p-1087606.html?rmmds=myorder